Heart disease remains the leading cause of morbidity and mortality in Western countries. While much is understood regarding development and treatment of ischemic heart disease, congenital cardiomyopathies are less understood. Dilated cardiomyopathy (DCM) is a form of heart disease that is characterized by ventricular dilation and systolic dysfunction. About 25-35% of DCM diagnoses are the result of inherited mutations in contractile proteins such as cardiac troponin T (cTn-T), which often culminate in early onset heart. Deficient calcium uptake due to decreased expression and activity of SERCA2a is a well-described hallmark of heart failure, and restoration by gene transfer has been shown to be effective in restoring contractility to human DCM iPSC derived cardiomyocytes (iPSC-CMs) to levels similar to that observed in control iPSC-CMs. Modeling DCM in patient hiPSCs offers an unprecedented opportunity to define the connection between the disease- causing mutation and the balance between adaptive and maladaptive signaling that dictates disease susceptibility and progression that at present are poorly understood. A high-throughput unbiased screen against a SERCA2a-eGFP reporter plasmid resulted in 144 microRNA (miR) hits that downregulated eGFP expression by >30%. These miRs were validated in a 5-point dose response assay and 82 were confirmed for their activity against SERCA2a. I have also profiled the expression of over 1000 miRs in human congenital DCM iPSC-CMs as compared to control iPSC-CMs from non-DCM family members. miRs found to be upregulated in DCM patient CMs were cross-referenced with those that target SERCA2a. The 23 miRs that met these criteria are now being tested for their effect against endogenous SERCA2a in control iPSC-CMs by calcium transient kinetic analysis and western blot. miRNA inhibition using anti-sense antagomiRs is also being performed in DCM hiPSC-CMs to improve endogenous SERCA2a and contractile function. miRs that show the most impressive results will be prioritized for in vivo inhibition in a mouse model of DCM. To test in vivo whether blocking pathologically upregulated miRNAs has a beneficial effect on SERCA2a expression and cardiac contractility, DCM mice will be administered a cocktail of the most potent angatomiRs, as judged by in vitro readouts. Mice will be monitored by echocardiogram every week for 3 months at which point hemodynamic analyses will be performed to determine PV loops and ESPVR. SERCA2a protein levels will be determined via western blot of cardiac tissue and histological sections will be analyzed for quantification of fibrosis and cells size relative to scramble sequence control antagomiR. The expectation is that DCM mice receiving a specific antagomiR cocktail will show enhanced cardiac function as compared to DCM mice receiving an inert control, and that the antagomiR cocktail may constitute a novel therapeutic option for the treatment of DCM.